Forest Floor Mystery: Pellets? Old Scat? Cache?

Lying at the base of a large Eastern Hemlock I recently found two piles of bleached bones. One pile consisted of mostly vertebrae; the other pile had numerous tibias, humeri and ribs. All were the appropriate size and shape to have come from several Eastern Chipmunk skeletons – at least four or five. How did they end up in two distinct piles?

The lack of any fur indicated that regardless of how these bones came to be here, they were deposited quite a while ago. The lack of any partial skulls or jaw bones and the large number of bones in each pile led me to believe that these were not the remains of two pellets that had been regurgitated by resident Barred Owls. No wild owl pellet I’ve ever dissected, including the large pellets cast by Snowy and Great Gray Owls, has contained even half this many bones, and most contained at least part of a jaw bone.

If not pellets, then scat? How likely is it that a predator could catch and consume multiple chipmunks rapidly enough so that they would end up in the same pile of scat? One feasible explanation could be that a fox, coyote or fisher preyed on young, inexperienced chipmunks, but the bones were adult-size bones.

Perhaps these two piles are the remains of a predator’s cache – perhaps a bobcat?

The possibilities are endless as to how this chipmunk graveyard came to be. However, none of the theories proposed here can explain the dissimilarity between the types of bones in each pile. If any naturally curious readers have insight into this phenomenon, your thoughts are welcome!

I have to agree with Janet. After seeing many groups of school kids dissect pellets, they naturally sort bones by size. If you are lucky enough to find a skull, that’s your easiest way to ID the remains. I think you found a pellet site after another human had dissected them. Great mystery! Thanks.

A dumped stew pot or anatomist’s brew? Most of the bones from a dumped pot or bowl would come out in the first dumping, with a second effort to get the small bones that might remain in the curve . While the bones look bleached and aged, they seem to have almost no debris on them, implying the piles are more recent then not.

Could it perhaps be a weasel? They keep heads as trophies (weird, I know) lining them up in their burrow, which might explain why you found no skulls. And they just might be into dissecting the parts, too? A great mystery!

Not sure but your picture bears a remarkable similarity to one I took in April when there was still a fair amount of snow on the ground in places. Mine had some fur and jawbones and is actually entirely on a red oak leaf that I was holding in my hand when I took the picture. It was also at the base of an Eastern Hemlock. I assumed it was a barred owl pellet that had degraded a bit. You can estimate the scale by some of the hemlock needles in the picture. I think the bones in my picture were probably mice rather than chippies.

I think the relatively undamaged bones in your picture makes it more likely to be something regurgitated rather than excreted. Do you have great horned owls in your area? Maybe a bobcat or coyote that ate a bunch of chippies and then threw up? My dogs and cats do that periodically.

Hi Peter, THanks so much for your input. I tend to think you are right about the pristine condition of the bones – the separation of the types is puzzling, as is the number of bones, for a pellet, but both of your theories seem the most plausible to me. WordPress does not allow for photos to come through. Could you possibly send yours to me at mholland@vermontel.net ? Thanks so much!

I have a frog skeleton sitting right in front of me, and I’m afraid I don’t concur…neither bones nor vertebrae are right. They are identical in size and shape to an eastern chipmunk’s, but that would have been a great explanation!

Hmmm…I know you’ve said it’s a place unlikely to have human visitors, but assuming you are human & did not take the photo using a telescope, it must be possible for a human to access it, unless perhaps it is gated, fenced, locked & topped with barb wire (e.g., on prison property) or constantly guarded by fierce watchdogs, or maybe immediately in your back yard or a friend’s who is normally at home & has intruder alarms, or was surrounded by sheer cliffs, it’s hard for me to imagine a place that would have trees & wild creatures but could not be reached by a budding naturalist.

One of my sons was tall, skinny, hiked up mountains, scrabbling up rock surfaces, bushwhacking, etc., by the time he was 12. I can imagine someone like that, perhaps some day to become a naturalist, or an orthopedic surgeon, or nature photographer, or writer, roaming in a difficult area, scouring for owl pellets, dried up dung, bones left behind by scavengers, etc. Perhaps making a number of finds with chipmunk bones & wanting to examine them, following a tendency to sort, at least roughly or for a while. Maybe even taking time to sketch or photograph some of them. Or visiting more than once. Maybe under the leaves a few yards away were some piles of bones from birds. Perhaps it was long enough ago that the bones have bleached & been cleaned since, & slid around a bit. Or were already clean, thanks to predators.

(I admit, I am thinking not only of my sons, but of myself, around 7 years old, finding a dead bird & using some sticks to dissect it. And my niece, in a heron rookery, closely examining — with her eyes only! — a dead chick that had fallen/been shoved from its nest, & caught on a low branch. She was in med school then.)

And the skull & jaw bones? Into her/his pockets for further examination at home. (After all, some folks are just… !!)

One more theory: Couple of turkey vultures scavenged a bunch of dead chippies killed by fishers or other weasels who stole the skulls. They then flew to your hemlock tree to roost and barfed up the bones in the middle of the night.